1. Field of the Invention
The present general inventive concept relates to a job assignment apparatus of an automatic material-handling apparatus to optimally assign a plurality of jobs to a plurality of vehicles using the Hungarian method of calculating an optimum solution of a matrix, and a method thereof.
2. Description of the Related Art
An equipment control process for controlling complicated equipment such as a semiconductor- or LCD-fabrication process is configured by interconnection of a variety of automatic material-handling systems (e.g., a plurality of stockers, an a OHT (Overhead Hoist Transport System), a OHS (Overhead Shuttle System), a RGV (Rail Guided Vehicle) system, and a AGV (Automatic Guided Vehicle) system), such that the material handling between the fabrication devices is implemented. The above-mentioned material-handling systems are controlled by their handling control systems.
The most important function of the control system is to optimally assign a plurality of jobs to a plurality of vehicles.
Generally, with the increasing capacity of the equipment fabrication process, the number of vehicles of the equipment fabrication process is greater than the number of jobs of the equipment fabrication process.
The above-mentioned problem of assigning a plurality of jobs to a plurality of vehicles is considered to be an NP-hard (Non-deterministic Polynomial-time hard), such that it is impossible to solve the problem by arranging all the cases.
There are a variety of conventional methods for assigning a plurality of jobs to a plurality of vehicles, for example, a priority-based assignment method, a job assignment method closest to the vehicle, an idle assignment method, and a heuristic assignment method, etc.
Indeed, most systems have difficulty in employing the above-mentioned conventional methods, and have been limited to provide only a local optimum solution of a specific range, instead of a global optimum solution.